The present invention relates to a circularly polarizing plate, particularly, to a circularly polarizing plate having an optically anisotropic layer containing a twisted aligned liquid crystal compound.
The present invention also relates to a retardation plate for a circularly polarizing plate used for the aforementioned circularly polarizing plate and relates to an organic electroluminescence (EL) display apparatus.
Retardation plates are extremely versatile and are used for reflective LCDs, transflective LCDs, brightness enhancement films, organic EL display apparatuses, touch panels, and the like. For example, since organic EL devices have a structure in which layers having different refractive indices are laminated on each other or a structure which uses metallic electrodes, external light is reflected from the interfaces between the respective layers, and this leads to problems such as a decrease in contrast or reflection in some cases. Therefore, conventionally, in order to suppress negative effects caused by the reflection of external light, a circularly polarizing plate constituted with a retardation plate and a polarizing film is used for organic EL display apparatuses, LCD display apparatuses, and the like.
Regarding a retardation plate used for a circularly polarizing plate, for example, as described in JP 3174367 B, the use of a retardation plate constituted with a λ/2 plate and a λ/4 plate is known.